CN115324554A - Evaluation and optimization method for severity of drill stick-slip vibration - Google Patents
Evaluation and optimization method for severity of drill stick-slip vibration Download PDFInfo
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Abstract
The invention discloses a method for evaluating and optimizing the severity of drill stick-slip vibration, which comprises the following steps of firstly, acquiring necessary parameters for evaluating the severity of drill stick-slip vibration based on an actual application scene; then establishing a relation graph of the rotating speed of the rotating disc and the time in the time domain and a relation graph of the rotating speed of the drill bit and the time, and judging the motion state of the drill bit in the specified time range; when the motion state is stick-slip, a stick stage and a slip stage in the relation between the rotating speed and the time are determined; respectively calculating the severity of the viscous stage and the severity of the slipping stage, and further calculating to obtain an evaluation index value of the severity of the viscous-slip vibration; evaluating the severity of the stick-slip vibration according to the evaluation index numerical result of the severity of the stick-slip vibration obtained by calculation; repeating the steps under different drilling operation parameter conditions to obtain evaluation index values of the severity of the stick-slip vibration under different drilling operation parameter conditions; and adjusting the drilling strategy to obtain the optimal drilling operation parameters.
Description
Technical Field
The invention relates to the technical field of dynamics of deep well drilling strings in petroleum and natural gas engineering, in particular to a method for evaluating and optimizing the severity of stick-slip vibration of a drill bit.
Background
In the process of exploration and development of oil and gas resources of deep wells and ultra-deep wells, abnormal working conditions caused by drilling equipment, geological conditions, field operation and the like, such as stick-slip vibration caused by improper setting of drilling operation parameters, often occur, so that different degrees of damage are caused to a rotary table, a drill rod, a drill collar and a drill string system of a drill bit, and even the drilling equipment is scrapped. If the stick-slip severity of the drill string system cannot be effectively evaluated, namely whether the current parameters can continue drilling or not is judged, the problems that the drill bit is seriously abraded, the equipment is prematurely scrapped and the drilling efficiency is low are caused, the drilling cost and the drilling period are wasted, and even the property safety of the drilling equipment and the life safety of field personnel are influenced.
In EP2462315B1 a method of estimating the severity of downhole vibration of a drilling assembly is disclosed which provides an indication to the driller when stick-slip conditions are present in the field, but the model used to estimate the severity of the twist in this method simply considers the ratio of the difference between the maximum and minimum values at the downhole bit to twice the surface rotational speed. In the conference paper of SPE 177950, a stick-slip severity index is proposed, which is expressed by the ratio of the difference between the maximum rotation speed and the average rotation speed of the drill bit after low-pass filtering to the average rotation speed on the ground, which is similar to the method for detecting the torsional vibration of the drill string disclosed in the invention patent of CN 107229599B. In patent CN109322653B, a ground stick-slip index is obtained by multiplying an average value of ground rotation speeds within a preset time interval by a difference value between a maximum value and a minimum value of a torque, and then dividing the difference value by an average value of 120 times of the ground torque, and when the obtained value is less than 0.4, determining the value as stick-slip, and when the value is more than 0.4, determining the value as whirl, and not giving a normal working condition and how to determine the severity of an abnormal working condition. An indicator TSE, which is the ratio of the difference between the maximum rotational speed and the average rotational speed of the drill bit to the average rotational speed of the drill bit, is also mentioned in the conference paper by SPE 163420. A system for monitoring downhole dynamic parameters is provided in patent CN111379550A, in which the minimum rotation speed is subtracted from the maximum rotation speed of a drill collar and then divided by the average rotation speed of the drill collar as an evaluation index SS of the stick-slip severity. In the six patents and papers, the stick stage and the slip stage of stick-slip vibration are not considered respectively, and the influence of the ground rotating speed and the bit rotating speed on the stick-slip severity of a drill string system is not considered in some patents and papers, so that the evaluation indexes have certain limitations, and the severity of vibration cannot be well represented from the two stages of stick-slip.
In patent WO2016081246A1, a system and a method for reducing stick-slip are proposed, which utilize a ground control unit to realize adjustment control on a torque value of a ground driving unit, so as to reduce a stick-slip oscillation frequency at a current time compared with a previous time. In the patent of US9581008B2, a method and apparatus for damping stick-slip vibration in a drill string is proposed, which relies on a PI controller to achieve adjustment of the rotational speed and frequency of a drilling mechanism, and avoid a drill string system from generating a large amount of torsional energy near the frequency of the stick-slip vibration, thereby minimizing the stick-slip vibration of the drill string. This is similar to the patent of invention with patent number CN106545327B, which discloses an intelligent driller control system, and the control system aims at providing an optimized control function for a ground driller. JP5571346B2 proposes a stick-slip detection device and a detection method for detecting stick-slip in a contact sliding section device having a regulator valve or a gas regulator. The invention patent with the patent number CN109138973B discloses an observation method for diagnosing stick-slip vibration of a drill string, and the motor driving parameters and a mathematical model are combined to judge the motion rule of a downhole drilling tool assembly and the torque of the drill string. The five patents can detect and find the stick-slip vibration or inhibit the stick-slip vibration by adjusting the drilling parameters, but the evaluation of the stick-slip vibration at the underground drill bit of the drill string system during the deep well drilling cannot be realized.
In summary, there is a need for a method for evaluating and optimizing the severity of stick-slip vibration of a drill bit, so as to determine whether the drill bit is stick-slip, quantify and characterize the severity of stick-slip vibration, recommend a drilling strategy matching the severity, and ensure drilling safety and drilling efficiency.
Disclosure of Invention
Aiming at the defects of the existing stick-slip vibration detection method, the invention provides a method for evaluating and optimizing the severity degree of the stick-slip vibration of a drill bit.
The invention provides a method for evaluating and optimizing the severity of stick-slip vibration of a drill bit, which comprises the following steps of:
s1, acquiring necessary parameters for evaluating the severity of stick-slip vibration of the drill bit based on different actual conditions of various application scenes of on-site actual drilling, indoor tests and computer simulation. The necessary parameters include: the average rotating speed value of the rotary table, the maximum rotating speed value of the drill bit in the viscous stage, the minimum rotating speed value of the drill bit in the viscous stage and the maximum rotating speed value of the drill bit in the slip stage in the specified time range.
And acquiring the necessary parameters through a driller control platform and a field stick-slip recording device in the application scene of the field actual drilling. In the application scene of the indoor test, the necessary parameters are obtained through a rotating speed sensor at the input motor and a rotating speed sensor at the drill bit. Under the application scene of computer simulation, the structural parameters of the drill string system are calculated according to the parameter information of the rotary table, the drill rod, the drill collar and the drill bit, wherein the structural parameters of the drill string system comprise the rotary inertia, the torsional rigidity and the torsional damping of the rotary table, the drill rod, the drill collar and the drill bit, and are used for deducing a motion differential equation of the drill string system to obtain the necessary parameters. The results of the three application scenario methods have a small amount of differences, but the differences are all within an acceptable error range, so that a specific mode needs to be selected according to the application scenario, the actual requirements and the implementation difficulty.
S2, establishing a relation graph of the rotating speed of the rotating disc and the time in the time domain and a relation graph of the rotating speed of the drill bit and the time, and judging the motion state of the drill bit in the specified time range according to the two relation graphs. The motion state comprises a stable state and a stick-slip state. The method for judging the stable state and the stick-slip state comprises the following steps:
the steady state of the drill bit is characterized in that the relationship between the rotating speed and the time of the drill bit is represented as that the rotating speed of the drill bit greatly fluctuates in an initial certain time, then the fluctuation range of the rotating speed of the drill bit is gradually reduced, and finally the rotating speed of the drill bit is gradually stable and close to the rotating speed of the rotary table.
The stick-slip state of the drill bit is characterized in that the relationship of the rotating speed and the time of the drill bit shows that a stick-slip stage and a slip stage of the drill bit alternately appear in a reciprocating mode, the stick-slip stage is characterized in that the amplitude of the rotating speed of the drill bit is low, the fluctuation frequency is high, and a negative value occasionally exists, and the slip stage is characterized in that the amplitude of the rotating speed of the drill bit is higher than the rotating speed of the rotary table.
When the motion state is stick-slip, the stick stage and slip stage in the relation of the rotating speed and the time are defined.
And S3, respectively calculating the severity of the viscous stage and the severity of the slipping stage, and superposing the viscous stage and the slipping stage to obtain an evaluation index value of the severity of the stick-slip vibration. The method comprises the following specific steps:
s31, calculating the severity of the viscous stage, wherein the formula is as follows:
where STI represents the severity of the sticking phase, RPM bit-stick-max Representing the maximum bit speed in the viscous phase, RPM bit-stick-min Representing the minimum value of the bit speed, RPM, during the viscous phase sur-avg Represents the average value of the rotating speed of the rotating disc;
s32, calculating the severity of the slipping stage, wherein the formula is as follows:
where SLI represents the severity of the slip phase, RPM bit-slip-max Representing the maximum value of the bit speed, RPM, during the slip phase sur-avg Represents the average value of the rotating speed of the rotating disc;
and S33, adding the severity STI of the viscous stage and the severity SLI of the slipping stage to obtain an evaluation index value SSVS of the severity of the viscous-slip vibration. Namely, it is
S4, evaluating the severity of the stick-slip vibration according to the SSVS calculated in the previous step; the calculation result takes 1 as a boundary, SSVS between 0 and 1 represents that the drill bit is in a stable state, and greater than 1 represents that the drill bit generates stick-slip vibration; the larger the SSVS value, the more severe the stick-slip vibration.
S5, repeating the steps S1-S4 under the conditions of different drilling operation parameters (such as drilling pressure and rotating speed) to obtain evaluation index values of the severity of the stick-slip vibration under the conditions of different drilling operation parameters; and further adjusting the drilling strategy according to the evaluation index values and the variation trend under different drilling operation parameter conditions to obtain the optimal drilling operation parameters.
According to evaluation index values and variation trends under different drilling operation parameter conditions, the drilling strategy is adjusted to obtain the optimal drilling operation parameters, and the specific method comprises the following steps:
and dividing different vibration states according to the numerical value and the expression form of the evaluation index and taking corresponding operation.
When the evaluation index value SSVS is less than 1, the drill bit can stably run, and the current drilling operation parameters are kept unchanged.
When the evaluation index value SSVS is 1-1.25, the drill bit shows torsional oscillation with low frequency and high frequency mixed, a drill string system is slightly influenced, and drilling operation parameters in a stable running state can be slightly adjusted.
When the evaluation index value SSVS is 1.25-1.7, the drill bit is completely stick-slip, and the safety of the drilling equipment needs to be noticed and the drilling operation parameters in a stable operation state need to be adjusted.
When the SSVS is more than 1.7, the drill bit is in a state of mixing complete stick-slip and high-frequency torsional oscillation, the property safety of the drilling equipment and the life safety of field personnel are affected, the drilling needs to be stopped, and the drilling operation parameters in a stable running state are adopted for re-drilling after the maintenance equipment confirms no problem.
Compared with the prior art, the invention has the advantages that:
(1) The invention is suitable for various application scenes of oil and gas well engineering. The method provided by the invention can adopt a proper mode to obtain required parameters according to different actual conditions of on-site actual drilling, indoor tests and computer simulation, and finally evaluate the severity of the stick-slip vibration of the drill bit.
(2) The method can evaluate the stable state and the stick-slip state of the drill bit and quantitatively represent the severity of stick-slip vibration of the drill bit. The result of the evaluation index is defined by 1, the value between 0 and 1 represents the stable operation of the drill bit, and the value greater than 1 represents the stick-slip vibration of the drill bit.
(3) The invention fully considers the viscous stage and the slipping stage of the drill stick-slip vibration. The viscous stage explains the fluctuation range of the angular speed of the drill bit, and emphasizes the wear of the teeth of the drill bit; and in the slippage stage, the rotating speed of the drill bit exceeding the rotating speed of the rotary table is clarified, and the tooth breaking of the drill bit is reflected.
(4) The invention can adjust the drilling strategy according to the drilling working condition and provide proper drilling operation parameters. Different vibration states are defined by means of evaluation indexes, and various drilling strategies including maintaining an original state, adjusting parameters and stopping drilling for inspection are adopted, so that the safety and the efficiency of drilling are guaranteed.
(5) The evaluation index of the severity of stick-slip vibration provided by the invention has the advantages of simple structure, easy understanding and convenient implementation. Under different application scenes, corresponding parameters can be obtained by adopting corresponding equipment, sensors and formulas, and the severity of the stick-slip vibration can be evaluated.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a flow chart of a method for evaluating and optimizing the severity of stick-slip vibration of a drill bit according to the present invention.
Fig. 2, a schematic diagram of the drill bit gradually entering steady state at initial start-up.
Fig. 3 is a schematic diagram showing a stick-slip state of the drill bit.
Fig. 4 is a graph showing the evaluation results of the severity of stick-slip vibration.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
As shown in FIG. 1, the method for evaluating and optimizing the severity of stick-slip vibration of a drill bit provided by the invention comprises five steps: (1) Determining necessary parameters for evaluating stick-slip based on actual application scenarios; (2) Establishing a relation between the rotating speed and the time, and judging the motion state of the drill bit; (3) Calculating the severity of the viscous stage and the slipping stage, (4) quantifying and representing the severity of the viscous-slip vibration by utilizing the evaluation indexes; (5) And according to the result of the severity of the stick-slip vibration displayed by the evaluation index, properly adjusting the drilling strategy and optimizing the drilling operation parameters.
The method is specifically described in the following by combining a drill string dynamic simulation model of a 5000m deep well in the northward block:
acquiring necessary parameters for evaluating the severity of the stick-slip vibration of the drill bit based on different practical conditions of various application scenes of on-site actual drilling, indoor tests and computer simulation. The necessary parameters for evaluating the severity of the drill stick-slip vibration are acquired and comprise the average rotating speed value of the rotary table, the maximum rotating speed value of the drill in the viscous stage, the minimum rotating speed value of the drill in the viscous stage and the maximum rotating speed value of the drill in the slip stage within a specified time range. One of the three ways of obtaining the parameters may be selected for use, and practical applications of the three ways are as follows:
in the embodiment 1, necessary parameters for evaluating the severity of drill bit stick-slip vibration are obtained based on data of on-site actual drilling, the average value of the rotating speed of the rotary table within a specified time range is obtained through the driller control platform, the maximum value of the rotating speed of the drill bit in the viscous stage, the minimum value of the rotating speed of the drill bit in the viscous stage and the maximum value of the rotating speed of the drill bit in the slip stage within the specified time range are obtained through the stick-slip recording device, for example, under the conditions of input bit pressure of 160kN and rotating speed of 60r/min, the average value of the rotating speed of the rotary table RPM is obtained within the time range of 600s through the driller control platform sur-avg At 58r/min, the maximum RPM of the drill bit in the viscous phase is obtained within the time range of 600s by means of a stick-slip recording device bit-stick-max At 53r/min, the minimum value RPM of the drill bit in the viscous stage bit-stick-min At-6 r/min, maximum bit speed RPM in slip stage bit-slip-max Is 106r/min.
In example 2, the parameters necessary for evaluating the severity of drill bit stick-slip vibration were obtained by laboratory tests, the average value of the rotational speed of the rotary table in a specified time range was obtained by the rotational speed sensor at the input motor, the maximum value of the rotational speed of the drill bit in the viscous phase, the minimum value of the rotational speed of the drill bit in the viscous phase and the maximum value of the rotational speed of the drill bit in the slip phase in the specified time range were obtained by the rotational speed sensor at the drill bit, for example, the current signal or the voltage signal was converted into a rotational speed signal by the rotational speed sensor at the input motor under the conditions of, for example, the bit weight of 160kN and the rotational speed of 60r/min, or the rotational speed information was directly extracted, and the average value of the rotational speed of the rotary table RPM was obtained in a time range of 600s sur-avg At 57.5r/min, the maximum RPM of the drill bit in the viscous phase is obtained in the time range of 600s by means of a stick-slip recording device bit-stick-max 52.9r/min, minimum bit RPM in viscous phase bit-stick-min Is-6.5 r/min, and the maximum bit speed RPM is obtained during the slip-off phase bit-slip-max Is 105.95r/min.
In example 3, the structural parameters of the drill string system were calculated by computer simulation based on the parameter information of the rotary table, the drill pipe, the drill collar and the drill bit, and the calculation results are shown in table 1 below. The structural parameters of the drill string system comprise the rotational inertia, the torsional rigidity and the torsional damping of the rotary table, the drill rod, the drill collar and the drill bit, and are used for deducing a motion differential equation of the drill string system, namely a formula (1), and finally the necessary parameters are obtained.
In the formula: j. the design is a square rs ，J dp ，J bh ，J bb The moment of inertia, kg · m, of the rotary table, drill pipe, BHA and drill bit, respectively 2 ；
Angular acceleration, rad/s, of rotary table, drill pipe, BHA and drill bit, respectively 2 ；K rd ，K db ，K bb Spring torsional stiffness, N.m/rad, between the rotary table and the drill stem, between the drill stem and the BHA, and between the BHA and the drill bit; theta rs ，θ dp ，θ bh ，θ pb Angular displacement, rad, of the rotary table, drill pipe, BHA and drill bit, respectively; c rd ，C db ，C bb Spring torsional damping, N.m.s/rad, between the rotary table and the drill stem, between the drill stem and the BHA, and between the BHA and the drill bit, respectively;
the angular velocities, rad/s, of the rotary table, drill pipe, BHA, and drill bit, respectively;
TABLE 1 drill string System structural parameters
In the three embodiments, necessary parameters for evaluating the severity of stick-slip vibration of the drill bit are obtained based on different actual conditions of various application scenarios of on-site actual drilling, indoor tests and computer simulation, and required parameters can be obtained in an appropriate mode according to the actual conditions. The indoor experiment is a result obtained after secondary influence factors such as well wall collision friction are simplified, the operation is convenient, the phenomenon of stick-slip vibration of the drill bit can be reflected, and a small amount of errors exist between the stick-slip vibration phenomenon and real underground conditions. The computer simulation is a calculation result of a theoretical model, is easy to implement, obtains a result quickly, has little error and can effectively reflect the severity of the stick-slip vibration of the drill bit. However, the difference of the error values between the results of the three modes is within an acceptable error range, and the influence on the final evaluation and optimization results is small and can be ignored. Therefore, in practical application, a mode can be selected according to actual conditions to obtain the necessary parameters for evaluating the severity of the stick-slip vibration of the drill bit.
And (II) establishing a rotating speed-time relation of the rotating disc and a rotating speed-time relation of the drill bit in a time domain, and judging the motion state of the drill bit in a specified time range. When the motion state is stick-slip, a stick stage and a slip stage in the relation of rotating speed and time are defined.
Fig. 2 is a schematic diagram of the drill bit gradually entering a steady state at an initial start-up stage, as shown in fig. 2. The input conditions for this diagram are weight on bit 160kN and rotational speed 100r/min. The steady state of the drill bit is characterized in that the relationship between the rotating speed and the time of the drill bit is represented as that the rotating speed of the drill bit greatly fluctuates in an initial certain time, then the fluctuation range of the rotating speed of the drill bit is gradually reduced, and finally the rotating speed of the drill bit is gradually stable and close to the rotating speed of the rotary table.
As shown in fig. 3, fig. 3 is a schematic view of the stick-slip state of the drill bit. The input conditions for this diagram are a weight on bit of 160kN and a rotational speed of 60r/min. The stick-slip state of the drill bit is characterized in that the rotation speed-time relation of the drill bit shows that a stick-slip stage and a slip stage of the drill bit alternately appear in a reciprocating mode, the stick-slip stage is characterized in that the rotation speed amplitude of the drill bit is low, the fluctuation frequency is high, and a negative value occasionally exists, and the slip stage is characterized in that the rotation speed amplitude of the drill bit is higher than the rotation speed of the rotary table.
And (III) respectively calculating the severity of the viscous stage and the severity of the slipping stage, and superposing the viscous stage and the slipping stage to calculate the severity of the stick-slip vibration within a specified time range to obtain an evaluation index value of the severity of the stick-slip vibration.
According to the formula
And calculating the severity of the viscous stage, and using the formula to clarify the fluctuation range of the angular speed of the drill bit in the viscous stage to represent the fatigue damage of a drill string system and the abrasion condition of the drill bit teeth. The input conditions were the aforementioned weight on bit 160kN and the rotational speed 60r/min, at this time RPM bit-stick-max 52.16r/min, RPM bit-stick-min At-6.94 r/min, RPM sur-avg Is 57.22r/min. The STI found by the equation is about 0.513.
According to the formula
And calculating the severity of the slippage stage, and using the formula to clarify the magnitude of the angular speed of the drill bit exceeding the rotating speed of the rotary table and represent the stress concentration of local areas of each structural connection part of the drill column system and the tooth breaking condition of the drill bit. The input conditions were the weight on bit (160 kN) and the rotational speed (60 r/min) as described above, at RPM bit-slip-max 105.9r/min, RPM sur-avg Is 57.22r/min. SLI is found to be about 0.85 by the equation.
And superposing the severity of the viscous stage and the severity of the slipping stage to obtain an evaluation index of the severity of the viscous-slip vibration within a specified time range. Under the input conditions of the bit pressure of 160kN and the rotating speed of 60r/min, the results of STI and SLI are added to obtain an evaluation index SSVS of the severity of the stick-slip vibration in a specified time range, and under the input conditions, the final result of the severity of the stick-slip vibration is about 1.363.
And (IV) quantitatively representing the severity of the stick-slip vibration by utilizing the evaluation indexes, wherein the calculation result takes 1 as a boundary, a drill bit is in a stable state between 0 and 1, and the drill bit generates the stick-slip vibration if the calculation result is larger than 1. The larger the calculation result of the evaluation index is, the more serious the stick-slip vibration is represented.
In the embodiment, under the input conditions of the bit pressure of 160kN and the rotating speed of 60r/min, the severity of the stick-slip vibration is represented quantitatively to be 1.363 which is greater than 1 by utilizing the evaluation index, which represents that the drill bit generates the stick-slip vibration.
And fifthly, inputting drilling operation parameters (such as drilling pressure and rotating speed) under different conditions, repeating all the steps to obtain a plurality of groups of evaluation index values under the input conditions, properly adjusting the drilling strategy according to the quantitative values and the variation trend of the evaluation indexes, and selecting proper drilling operation parameters.
And (3) expanding the input conditions to a drilling pressure of 120kN to 220kN, a gradient of 20kN, a rotating speed of 40r/min to 100r/min and a gradient of 20r/min, and repeating the operations from the step 1 to the step 4 to obtain a plurality of groups of evaluation index values under the input conditions, as shown in fig. 4, wherein fig. 4 is an evaluation result graph of the severity of the stick-slip vibration.
And when the numerical value is less than 1, namely the evaluation index with a blank background in the figure 4, the drill bit can stably run and the current drilling operation parameters are kept unchanged. When the numerical value is 1 to 1.25, namely the background in fig. 4 is an evaluation index of a gray slope, the drill bit shows torsional oscillation of low frequency and high frequency, the drill string system is slightly influenced, and the drilling operation parameters in a stable operation state can be slightly adjusted. When the value is 1.25 to 1.7, i.e., the background in fig. 4 is an evaluation index of light gray filling, the drill bit exhibits complete stick-slip, and it is necessary to pay attention to the safety of the drilling equipment and to adjust the direction of the drilling operation parameters in a steady operation state. When the value is larger than 1.7, namely the background in fig. 4 is an evaluation index of dark gray filling, the drill bit is in a state of mixing complete stick-slip and high-frequency torsional oscillation, the property safety of the drilling equipment and the life safety of field personnel are affected, the drilling needs to be stopped, and the drilling operation parameters in a stable operation state are adopted for re-drilling after the maintenance equipment confirms that no problem exists.
Therefore, the severity of the stick-slip vibration of the drill bit can be visually evaluated by the method and a corresponding optimization method is provided, taking fig. 4 as an example, the medium-low drill press fit and the medium-high rotating speed are used as much as possible so as to ensure the stability of the drill bit and the drilling safety, the stick-slip vibration is effectively inhibited or even avoided by more than 90% by using the method, the mechanical drilling speed is improved by 30%, the drilling period is shortened by 30%, and the drilling cost is reduced by 30%.
In conclusion, the method for evaluating and optimizing the severity of the drill stick-slip vibration provided by the invention can be suitable for different application scenes, the emphasis points of the severity of the stick-slip vibration and the slip-off stage are fully considered, the severity of the stick-slip vibration of the drill bit is quantitatively represented, whether the current drilling operation parameters are safe or not and whether the drilling can be continued or not is evaluated, and how to adjust the drilling strategy is carried out, so that the proper drilling operation parameters are provided, and finally, the field drilling is guided to be safely and efficiently carried out.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A method for evaluating and optimizing the severity of stick-slip vibration of a drill bit is characterized by comprising the following steps:
s1, acquiring necessary parameters for evaluating the severity of stick-slip vibration of the drill bit; the necessary parameters include: setting the average rotating speed value of the rotary table, the maximum rotating speed value of the drill bit in the viscous stage, the minimum rotating speed value of the drill bit in the viscous stage and the maximum rotating speed value of the drill bit in the slippage stage within a specified time range;
s2, establishing a relation graph of the rotating speed of the rotating disc and the time in the time domain and a relation graph of the rotating speed of the drill bit and the time, and judging the motion state of the drill bit in a specified time range according to the two relation graphs; the motion state comprises a stable state and a stick-slip state; when the motion state is stick-slip, a stick stage and a slip stage in the relation between the rotating speed and the time are determined;
s3, respectively calculating the severity of the viscous stage and the severity of the slipping stage, and superposing the viscous stage and the slipping stage to obtain an evaluation index value SSVS of the severity of the viscous-slip vibration;
s4, evaluating the severity of the stick-slip vibration according to the SSVS calculated in the previous step; the calculation result takes 1 as a boundary, SSVS between 0 and 1 represents that the drill bit is in a stable state, and greater than 1 represents that the drill bit generates stick-slip vibration; the larger the evaluation index value is, the more serious the stick-slip vibration is;
s5, repeating the steps S1-S4 under different drilling operation parameter conditions to obtain a stick-slip vibration severity evaluation index value SSVS under different drilling operation parameter conditions; and further adjusting a drilling strategy according to the SSVS and the variation trend under different drilling operation parameters to obtain the optimal drilling operation parameters.
2. The method for evaluating and optimizing the severity of drill stick-slip vibration according to claim 1, wherein in step S1, the necessary parameters for evaluating the severity of drill stick-slip vibration are obtained by one of field drilling, laboratory tests and computer simulation.
3. The method for evaluating and optimizing the severity of drill stick-slip vibration as claimed in claim 1, wherein in step S2, the steady state and stick-slip state are determined by the following method:
and (3) steady state: the relation between the rotating speed of the drill bit and the time is shown in the way that the rotating speed of the drill bit greatly fluctuates in an initial time period, then the fluctuation range of the rotating speed of the drill bit is gradually reduced, and finally the rotating speed of the drill bit is gradually stable and close to the rotating speed of the rotary table;
stick-slip state: the relationship between the rotating speed and the time of the drill bit is shown in the way that a viscous stage and a slip stage of the drill bit alternately appear in a reciprocating mode, the viscous stage is characterized in that the amplitude of the rotating speed of the drill bit is low, the fluctuation frequency is high, and a negative value occasionally exists, and the slip stage is characterized in that the amplitude of the rotating speed of the drill bit is higher than the rotating speed of the rotary table.
4. The method for evaluating and optimizing the severity of drill stick-slip vibration according to claim 1, wherein step S3 is as follows:
s31, calculating the severity of the viscous stage, wherein the formula is as follows:
where STI represents the severity of the sticking phase, RPM bit-stick-max Representing the maximum bit speed in the viscous phase, RPM bit-stick-min Representing the minimum value of the bit speed, RPM, during the viscous phase sur-avg Represents the average value of the rotating speed of the rotating disc;
s32, calculating the severity of the slipping stage, wherein the formula is as follows:
where SLI represents the severity of the slip phase, RPM bit-slip-max Representing the maximum value of the bit speed, RPM, during the slip phase sur-avg Represents the average value of the rotating speed of the rotating disc;
and S33, adding the severity STI of the viscous stage and the severity SLI of the slipping stage to obtain an evaluation index value SSVS of the severity of the viscous-slip vibration.
5. The method for evaluating and optimizing the severity of stick-slip vibration of a drill bit as claimed in claim 1 wherein in step S5, the drilling operation parameters include weight-on-bit and rotational speed.
6. The method for evaluating and optimizing the severity of drill bit stick-slip vibration according to claim 5, wherein in step S5, the drilling strategy is adjusted according to the SSVS and the variation trend under different drilling operation parameter conditions to obtain the optimal drilling operation parameters, and the specific method is as follows:
when the SSVS is less than 1, keeping the current drilling operation parameters unchanged;
when SSVS is 1-1.25, the drilling operation parameters under the stable operation state can be adjusted in a small range;
when the SSVS is 1.25-1.7, the drill bit is completely stick-slip, and the safety of drilling equipment needs to be noticed and the drilling operation parameter direction under the stable operation state needs to be adjusted;
when the SSVS is more than 1.7, the drill bit shows a state of mixing complete stick-slip and high-frequency torsional oscillation, the drilling needs to be stopped, and the maintenance equipment adopts the drilling operation parameters under the stable running state to re-drill after confirming no problem.
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